Stator casing construction for gas turbine engines



D. R. DAVIS June 13, 1967 STATOR CASING CONSTRUCTION FOR GAS TURBINE ENGINES Filed April 28, 1965 2 Sheets$heet INVENTOR. flW/fl 5. 041 45 D. R. DAVIS June 13, 1967 STATOR CASING CONSTRUCTION FOR GAS TURBINE ENGINES Filed April 28, 1965 2 Sheets-Sheet 2 We W United States Patent C 3,325,087 STATOR CASING CONSTRUCTION FOR GAS TURBINE ENGINES David R. Davis, Cincinnati, Ohio, assignor, by mesne assignments, to the Unted States of America Filed Apr. 28, 1965, Ser. No. 452,457 7 Claims. (Cl. 230-114) This invention relates generally to a stator casing construction for gas turbine engines. More particularly, it pertains to a lightweight fabricated stator casing assembly having improved means strengthening the casing and securing stator vanes therewithin and to a method for constructing such a stator casing assembly. is

One of the primary objectives of designers of aircraft gas turbine engines is to achieve maximum strength consistent with weight, cost and reliability requirements. Accordingly, more and more use is being made of sheetmetal fabrications in aircraft jet engines, particularly in the construction of the supporting structures, such as the compressor or turbine startor casings. As is well known, these stator casings house relatively high speed rotating parts, the compressor casing, in particular, housing an axial-flow multi-stage rotor having a plurality of rows of airfoils or blades which act in conjunction with interspersed rows of stator airfoils or vanes to raise the pressure of the motive fluid (air) passing through the compressor. An example of this type of apparatus is shown and described in the patent to Howard, 2,610,786, assigned to the present assignee.

In more modern jet engines than that shown in the aforementioned Howard patent, it is desirable to provide means for varying the angle of attack of the stator vanes, in particular, to compensate for decreased stall margin or, i.e., take advantage of, the increased ram (inlet) air pressure with increased flight speeds. Examples of jet engine compressors of axial-flow variable stator vane design will be found in the patents to Neumann, 2,933,234, and Balcom et al., 2,936,108, both assigned to the present assignee. As more fully explained in Balcom et al., more power can be obtained from a gas turbine engine by providing a higher pressure ratio compressor for the engine. However, whenever a conventional high pressure ratio compressor with fixed stator vanes is used, stall characteristics occur during various part speed conditions. This is due to the fact that when a compressor is designed for a high speed, high pressure operating condition, the stator vanes are designed to have a particular angle of attack to give the most efiicient operation at that particular operating condition. During starting or at some part speed condition, the angle of attack of the front rows of vanes will become mismatched from the rows of vanes in the rear of the compressor if the startor vanes are fixed, and, thereby create stall. In other words, at the part speed or starting condition, the rear stages cannot take the quantity of air that is being passed to it by the front stages. Accordingly, back pressure is built up so as to choke the compressor. In order to prevent this stall characteristic from occurring, adjustable stator vanes can be provided so that at the starting or part speed condition the front stages can be closed down with respect to the rear stages and thereby provide the correct airfoil orientation angle for the particular velocity of flowing air. By this means, the operating characteristics of the compressor are improved under certain operating conditions since the direction and quantty of air flow is changed to correspond to the angle of attack of the stator vanes. This change in air flow has a direct bearing on the stall characteristics of an axial flow compressor.

By making an engine construction heavy enough from a. structural standpoint, the approach to the stall region 31,325,081 Patented June 13, 1967 ice of a compressor will not significantly effect its operation. For example, the approach to the .stall region of a compressor excites or creates pressure surges which result in large vibrations in the structural components of the compressor. If the structural members are sufiiciently heavy, they can withstand these large vibrations. However, a gas turbine engine having a good power to weight ratio results in an air frame having the capability of either carrying more gas or more pay load. A heavy stucturally built jet engine can not obtain this good power to weight ratio. However, in order to provide the best power to weight ratio of a jet engine it is very important that the engine be made as light as possible. The problem of approaching a stall region then takes on added significance. The use of variable stator vanes, therefore, While beneficial somewhat complicates the compressor aerodynamic and mechanical design problems, :but I have discovered that it also offers an opportunity to improve the construction of the stator casing.

It is thus a general object of this: invention to provide an improved lightweight fabricated stator casing assembly for gas turbine engines of the types having fixed and variable stator vanes.

A more specific object of this invention is to provide a fabricated casing construction for use in a multi-stage axial-flow jet engine compressor, in which improved means are incorporated that both strengthen the fabricated sheet-metal assembly and, at the same time, support the stator vanesv Another more specific object of this invention is to provide for use in a jet engine axial-flow compressor structure designed to give added strength to a sheet-metal outer stator casing wall while also providing a more easily fabricated, yet dimensionally accurate and relatively lower cost mechanism for variable stator vane support and actuation.

A further object of my invention is to provide a new and improved method for assembling a stator casing for a gas turbine engine of the type having fixed and variable stator vanes.

In carrying out my invention in one form thereof, I provide an improved stator assembly, the main structural member of which is a lightweight stator casing having a plurality of circumferentially spaced openings formedin it. A plurality of stator vanes are disposed within the casing and are provided with mounting studs which extend outwardly through the openings. At least one annular stiffening member is positioned around the casing for strengthening the casing against flexure during operation of the engine. The stifiening member has a plurality of openings radially aligned with the openings in the casing so as to accommodate the mounting studs of the stator vanes as they extend out of the casing, and, by my invention, an improved means is provided for both securing the stiffening member to the casing and for journaling the mounting studs of at least some of the stator vanes in the aligned openings of the stiffening member and the casing for relative turning movement with respect thereto..This means, in one preferred form thereof, comprises a plurality of pairs of inner and outer telescopically arranged bushing members which are located within and extend between the respectively aligned openings of the casing and the stiffening members. A flange is provided on both the inner and the outer bushing members, the flange on the outer member engaging the inner surface of the casing while the flange on the inner member engages the outer surface of the stiffening member. Further, the bushing members and each pair include interlocked circum- 'ferentially enlarged portions or collars at the outer casing bers, together with the inner and outer flanges both locks the bushing members in place on the casing and fixedly locates the stiffening member therearound. Additionally, the inner bushing members form journaling surfaces for rotatably mounting the studs of the variable stator vanes, and thereby my improved structure serves the dual function of. both strengthening the lightweight casing and mounting the variable stator vanes.

In a preferred method for forming the lightweight stator assembly, the bushing members are provided with sections of reduced thickness and these sections are collapsed outwardly by a compressive force applied to the bushing members so as to form the interlocking collars on the outer surface of, the casing.

Other objects and advantages of'the method and means of the invention will be apparent from the following detailed description and claims and from the accompanying drawings, all of which describe by way of illustration only and without limitation what is now considered to bea preferred embodiment of the-invention.

FIG. 1 is an exterior pictorial view of an axial-flow aircraft gas turbine including a compressor section constructed according to the invention.

FIG. 2 is an enlarged, partial view of the exterior of the compressor casing illustrating the placement of the casing stiffening means and the means for actuating the variable stator vanes.

FIG. 3 isan enlarged, exploded view, partially in crosssection, of the details of the casing wall strengthening and variable stator vane support means of the invention.

FIGS. 4 and 5 illustrate schematically a preferred method of assembly of means shown in FIG. 3.

FIG. 6 is an assembly view, in cross-section, of one of a row of variable stator vanes, illustrating the means for strengthening the sheet-metal casing and supporting the variable stator vanes, according to the invention.

FIG. 7 illustrates improved means for strengthening the casing. when the, casing is axially split along a horizontal line.

FIG. 8 illustrates conventional flange means.

Referring first to FIG. 1, indicated generally at 1 is an aircraft gas turbine engine having an axial-flow compressor 2. The compressor includes an inlet 3 through which motive fluid (air) is taken into the engine to be compressed by the compressor. The air then passes downstream from the compressor into combustion chamber 4 for burning with fuel to increase itsvelocity before it is passed through a turbine 5, at which point energy is taken out of the now hot gas stream to drive the compressor. The motive fluid finally is discharged in the form of a propulsive gas stream from a jet exhaust nozzle 6.

The compressor 2 includes a casing assembly, indicated generally at 10 in FIG. 2, having an outer wall 12 of relatively thin sheet-metal construction for reduced weight in keepingwith the design objectives of todays modern jet engines. The outer wall, as seen more clearly in FIG. 6, has an outer surface 14 and an inner surface 16, the latter forming the outer flow path boundary for confining the engine motive fluid. For. convenience of assembly and repair, particularly of the compressor, it may be desirable to form the casing 10 in sections along a horizontal split-line, indicated at 18. In this case, as illustrated, flange means, indicated generally at 20, are provided along the casing section edges for securely fastening the sections into a pressure tight vessel.

The axial-flow compressor includes a series of stages or rows of stator vanes, some of which are variable as shown at 22 in FIG. 6, followed by rows of rotating airfoils or blades, one of which is partially shown at 24. In the case of the variable stator vanes, in particular, it is desirable to provide support at the vane tip ends in the form ofannular shroud means, as indicated at 26. At the other end of the variable vanes 22, i.e., the stub or root ends, there is provided the improved variable vane supporting and easing stiflening means, of the present invention, indicated generally at 28 in the drawings. Means are provided for rotating the vanes 22 about their longitudinal axes, and this means includes a lever arm, indicated at 30. The lever arm 30 is loosely connected to an actuating member, in this case a half-ring 32, by a pin 34 threaded at one end to engage a nut 36. Control means (not shown) are provided to rotate the half-rings which are joined by means 38, as seen in FIG. 2. The half-rings rotate circumferentially about the casing for tangential movement of lever arms 30 and, thus, turning movement in a radial planeof the stator vanes. A complete control mechanism for varying stator vanes is more fully described in each of the aforementioned Neumann and Balcom patents.

As seen in detail in FIGS. 3 and 6, each vane root or stud end, indicated generally at 40, comprises a thrust bearing surface 42, a stub or platform portion 44 having a machined flat at 46, a reduced neck portion 48, and a threaded portion 50. The vane stub end is adapted to fit through a hole 52 provided in the casing wall 12, there being a circumferentially extending row of equi-spaced openings or holes to receive a row of vanes for each stage of the compressor.

Turning now more specifically to the improved strengthening and vane supporting means of the invention, the several components of a disclosed supporting means of the invention, the several components of a disclosed embodiment of the variable vane support and casing wall stiffening means 28 are shown in an enlarged exploded assembly view in FIG. 3, the components being shown fully assembled in FIG. 6. It will be understood that while the preferred form of the invention is illustratedusing a variable stator vane the invention will have equal utility for fixed, i.e., non-variable stator vanes. There is provided for each row of variable vanes 22 a stiffening member or band 54, preferably channel-shaped in cross-section for added rigidity. Band 54 includes a plurality of openings or holes 55 therethrough of approximately equal size to the casing holes 52. Holes or openings 52 and 54 are so spaced and arranged circumferentially of the band and wall members, respectively, as to form aligned outer and inner pairs of openings having their centers on the same radial line with respect to the casing axis. As the vane longitudinal axis will be substantially co-linear with the center line through a pair of such holes, vane centering is facilitated. There is thus little chance of binding or unnecessary friction as the angle of attack of the vane is varied with respect to the motive fluid as it flows through the compressor in the direction indicated by the large arrow in FIG. 6.

By my invention, means are provided to maintain the vane stub end 40 within the pairs of aligned holes while at the same time adding strength to the casing Wall in cooperation with the plurality of axially-spaced'stiflening bands 54. As indicated generally at 56, this means comprises a double spool or bushing assembly including telescopically arranged bushings or spool members 58 and 62. The bushing assembly includes a flange at each end thereof; specifically, in the illustrated embodiment an outer flange 64 is formed on the inner bushing 62 and an inner flange 60 is formed on the outer bushing 58. As seen in the drawings flanges 60 and 64 extendoutwardly and are preferably circular (annular), each having a diameter greater than the respective casing and band holes 52 and 54.

As will be more fully described hereinafter, the flanges 60 together with circumferentially enlarged interlocked portions 92a and 94a of the bushings and flange 64 secure the bushing assembly in the casing hole 52, and fixedly locate the stiffening band on the bushing assembly around the casing.

In accordance with a further aspect of the invention, means are provided to mount the stub end Within the double spool assembly. The mounting means include a fastening or cup fmember indicated generally at 66. Member 66 has a first recess or cavity 68 opening outwardly of the casing assembly, this outer cavity 68 including a seat portion 70. Inwardly of the seat portion is a second recess or cavity 72, which opens opposite to the first re cess, this second recess having a flat or keyed wall portion at 74. The recesses or cavities 66 and 72 are joined by a neck portion 76 adapted to pass the threaded portion 50 of the vane stub end. The cup or fastening member is machined at 80- to provide a seat for one end of lever arm 30. This end of the arm preferably includes a hole 82 adapted to fit closely on the seat 80 around its central boss where the arm may be secured by brazing, or an equivalent metal joining arrangement. Likewise, the other, or half-ring, end of lever arm 30 has a hole 8 for pin 34. Bearing means in the form of a carbon sleeve 86 and surface 86a are provided along with a washer 88 to facilitate relative movement between the cup member 66 and bushing assembly when they are assembled together socurely. The cup member is held in the bushing assembly by means of a controlled-torque nut 90 which is threaded on the vane stub portion 50 and which rests on inclined seat 76 in the outer recess or cavity 68. Use of the hole 82 and seat 80 arrangement facilitates use of the disclosed torque-controlled fastening means which is intended to prevent damage to the relatively expensive vanes 22. and somewhat fragile sheet-metal parts of the vane support and easing stiffening means 28.

It will be seen that when the casing assembly is completed as shown in FIG. 6, the variable stator vanes 22 are journaled by means of the bushing assembly 56. Specifically, the vanes are mounted with the cup members 66 and due to the engaging flats 46 and "74 on the vane stub member, respectively, the vane and cup members rotate together being journaled within the inner bushing 62. The carbon sleeve 86 serves to reduce the friction between the cup member and bushing.

Prior to final assembly of the variable stator vanes within the casing 10, and in accordance with a preferred embodiment of the method of constructing the improved lightweight stator casing assembly disclosed herein, it will be necessary to fixedly locate the stiffening means or hands 54 with respect to the casing. A preferred method of assembly is as follows. With the cylindrical sheet-metal wall member 12 formed and retained in a fixture, a number of pre'formed (in channel section) annular bands 54 are spaced axially along the casing wall and retained in another fixture so as to be concentric with the casing and radially spaced from the outer surface 14 of the wall 12. Preferably holes 52 and 54 are then drilled in the casing and band members, respectively, the drill being centered onradial lines with respect to the casing axis. Obviously, the drilling may be done from outside or inside the easing. Also, the holes could be appropriately dimensioned and located prior to fixturing the pieces and then aligned in pairs when the casing member and bands are brought together.

In any event, with the casing and band holes provided and aligned in pairs, pre-formed spool or bushing members 58 and 62, provided with circumferentially reduced wall portions at 92 and 94, respectively, are assembled with the fixtured casing and band pieces in the following manner. Spool or bushing member 58 is passed outwardly through the casing hole 52the non-flanged end firstuntil that end extends into the stiffening member opening 55, Le, until locating flange 60 abuts the inner surface 16 of the casing wall 12. The bushing will be cut off flush at the band 54 or, in the preferred arrangement, the length will have been predetermined by the spacing between the band and easing surface and the thickness of the band. Next, the second or inner bushing 62, sized to have an OD. just slightly smaller than the first bushing ID, is telescoped within the first bushing, the locating flange 64 at the outer end retaining the second bushing at the level of the band 54. Again, the inner or other end of the bushing is cut off, or the bushing is pre-formed to have the desired length. The reduced wall portions 92a and 94a located, respectively, adjacent the flanged end and the non-flanged end of bushing members 58 and 62, also respectively, will now be in juxtaposition. By application of equal but opposing forces the nestled bushing walls are now in a position to be collapsed-at the reduced portions thereofto fixedly locate the wall and stiffening band members with respect to each other. Thus, as shown in the schematic illustrations of FIGS. 4 and 5 force is applied parallel to the radial or hole center line (co-linear with the bushing center lines) to force the walls outwardly into the circumferentially enlarged collar configuration, indicated at 92a and 94a. In cooperation with flanges 60 and 64 this arrangement secures the bushing assembly and the sheet-metal annular stiffening band members 54 in place whereby the latter members stiffen the sheet-metal casing wall 12. To prevent unwanted stress and ensure the forces being applied are co-linear to the axis of the double bushing or spool assembly, die or arbor Y may be inserted in the inner bushing 62 for support of the inner bushing walls and the outer bushing flange 60 during the collapsing operation. In conjunction with the arbor, an annular or ring die X may be utilized which will be sized to apply force to the flange 64. The die X preferably will include a hole adapted to receive the arbor Y, as shown, for further ensuring the correct line of direction of the collapsing forces indicated by the large arrows in the drawings.

In order to further strengthen the casing wall when it is split at 18 to facilitate repair and assembly, by my invention there is provided a double H-shaped flange arrangement which may be used in combination with the stiffening bands 54, as shown in detail in FIGS. 5 and 6. Thus, flange means 20 comprises a mirror-image pair of generally U-shaped, in cross-section, flange members indicated generally at little-1011b for easing sections 10a and 1011, respectively. As shown, the flange members have thickened, generally triangular or web-shaped arms 102a- 104a and 10215-10417, respectively, the arms of each flange being joined by center sections 105a105b forming the bottom of the U- or, in abutment as shown in the drawings, the web of the H. The arms 104a and 1041) may be butt-welded to the casing section edges or brazed to the casing in an overlapping relationship, as shown. A nut 167 and bolt 108 fastening arrangement may be used to complete the assembly. The channel section band members are also brazed to the H-shaped flange assembly where the bands cross the split-line, as shown in FIG. 2.

The primary advantage of this arrangement is the elimination of the distortion phenomenon present in the usual flange design, i.e., simple L-shapcd flanges butted and joined by fastening means as shown in FIG. 8. In. the usual construction the pressure loads cause stresses tending to separate the heel of the flanges: at the casing splitline. Since the fastening means restrains the load, the result is a moment of force at the flange tending to distort the casing inwardly, as seen in dotted lines in FIG. 8. With the arangement shown in FIG. 7 on the other hand, the outer bands 54 are positioned by arms 102a-102b, substantially equal in size and strength to arms 10411-10412, which forces the outer bands to share the tensile pressure or hoop stresses. The resultant forces tend to be equalized in the direction shown by the arrows in FIG. 7. In this manner, the overturning moments and the resultant radial deflection of the casing wall is reduced or eliminated.

While particular embodiments of the means and method of the present invention have been disclosed, it will be obvious to those skilled in the art that various changes and modifications may be made in the embodiments thereof without departing from the spirit or scope of the invention, and it is therefore intended in the appended claims to cover all such equivalent variations and modifications.

What I claim and desire to secure by Letters Patent is:

1. In a gas turbine engine, a lightweight stator assembly comprising:

and means for both journaling the mounting studs of said vanes and securing said stiffening members to said casing, and means including a plurality of pairs of inner and outer telescopically arranged bushing members located Within and extending between the respectively aligned openings of said casing and said stiffening member, said pairs of bushing members each having a flange on the outer member thereof engaging the inner surface of the casing, a flange on the inner member thereof engaging the outer surface of the stiffening member, and interlocked laterally enlargedportions on both members of the pair on the outer surface of the associated opening in said casing, whereby said pairs of bushing members are locked in place and secure said stiffening member to said casing, with the inner bushing members forming journaling surfaces for rotatably mounting said studs of the stator vanes.

2. In a gas turbine engine, a lightweight stator assembly comprising:

astator casing member having a plurality of c1rcumferentially spaced openings formed therein;

a plurality of stator vanes disposed within said casing member and having mounting studs extending outwardly through said openings;

an annular stiffening member positioned around said casing member for strengthening said casing member, said annular stiffening member having a plurality of openings radially aligned with the openings in said casing member;

and means for both journaling the mounting studs of said'stator vanes and securing said stiffening member to said casing member, said means including bushing means located within the respectively aligned openings of said casing and said stiffening member, said bushing means having an inner flange engaging the inner surface of said casing member, an outer flange overlying said stiffening member, and collar means engaging the other surface of one of said members to secure said bushing means thereto, whereby said bushing means both attach said stiffening member to said casing and form journal surfaces for rotatably mounting said stator vanes.

3. In a gas turbine engine having a lightweight stator casing, means for strengthening said casing and securing a plurality of stator vanes therewithin, said means comprising:

an annular member having a plurality of circumferentially equi-spaced openings therein, said annular member being disposed about said casing in spaced relation therewith, said openings being radially aligned with a plurality of like openings in said casing;

a first elongated bushing member having a first outwardly-extending flange atone end thereof, said first bushing member extending through a pair of said aligned openings in said casing and said annular member, respectively, said first bushing member being located in said casing by said first flange;

a second elongated bushing member having an outwardly-extending flange at one end thereof, said second bushing member being nestled within said first bushing member and being located therewithin by said second flange abutting said annular member and the other end of said first bushing member, said inner and outer bushing members each having co-extensive outwardly-expanded wall portions in juxtaposition engaging the outer surface of said casing to enable said first and second flanges to fixedly locate said annular member with respect to said casing;

and means loosely received in said second bushing member and adapted to securely engage one end of a stator vane within said second bushing member for relative movement of said vane about its longitudinal axis with respect to said casing.

4. The apparatus described in claim 3 wherein said annular member comprises a stiffening band of shallow channel-shape, in cross-section, the channel being open inwardly towards said casing, and wherein said casing is split into substantially equal sections along its length, said casing sections having pairs of identical U-shaped mating flanges at the longitudinal edges thereof, the lateral portions of said flanges abutting along the lengths of said casing sections to form an H-shaped connection for said sections, and fastening means securing said U-shaped flanges together for improved casing internal pressure load distribution in combination with a plurality of said annular members joined thereto.

5. The apparatus described in claim 3 wherein the means received in said second bushing member includes a cylindrical cup member having a flange adjacent one end thereof, a first cavity opening outwardly away from the casing, a seat portion at the bottom of said first cavity, a second cavity opening inwardly toward said casing, said second cavity having a locating flat on a wall thereof, and a hollow neck portion joining said first and second cavities, said second cavity, said neck and said first cavity, respectively, receiving a stub end of a stator vane, said stub end including a threaded portion and a flattened portion adapted to register with said cavity flat for combined movement of said cup member and said vane relative to said bushing members, and nut means adapted to engage said threaded stub portion and contact said seat portion for retention of said vane stub end in said second bushing member.

6. In a jet engine:

an axial-flow compressor stator casing, said stator casing comprising a cylindrical wall member having at least one row of circumferentially equi-spaced openings arranged in a plane normal to the axis of said casing;

an annular stiffening member disposed about said casing in spaced relation to said cylindrical wall member, said annular stiffening member having a plurality of openings therein adapted to be radially aligned with the openings in said casing;

a first elongated bushing member having a first out wardly-extending flange at one end thereof, said first bushing member extending through a pair of said aligned openings in said casing and said annular stiffening member, respectively, said first bushing member being located in said casing by said first flange;

a second elongated bushing member having an outwardly-extending flange at one end thereof, said second bushing member being nestled within said first bushing member and being located therewithin by said second flange abutting said annular stiffening member and the other end of said first bushing member, said inner and outer bushing members each having co-extensive outwardly-expanded reduced wall portions engaging the outer surface of said casing to enable said first and secondflanges to fixedly locate said annular stiffening member wtih respect to said casing;

a plurality of stator vanes each having a tip end and a stub end, each of said vanes being positioned with its tip end projecting radially inwardly toward the casing axis and its stub end projecting radially outward through one of said casing openings into said second bushing member;

and means securing said vane stub end in said second bushing member including bearing means permitting relative movement between the vane and the bushing members as the vane is turned about its longitudinal axis.

7. In a jet engine:

an axial-flow compressor stator casing, said stator casing comprising a cylindrical wall member having at least one row of circumferentially equi-spaced openings arranged in a plane normal to the axis of said casing;

an annular stifiening member disposed about said casing in spaced relation therewith, said annular stiffening member having a plurality of openings arranged to form pairs of radially aligned openings in combination with respective openings in said casing;

a plurality of first elongated bushing members each having a first outwardly-extending flange at one end thereof, said first bushing members extending through said pairs of openings in said casing and said annular stiflening member, said first bushing members being located in said casing by said first flanges;

a plurality of second elongated bushing members each having a second outwardly-extending flange at one end thereof, one of said second bushing members being telescoped within each of said first bushing members and being located therewithin by said second flanges abutting said annular stiffening memher and the other ends of said first bushing members, said inner and outer bushing members having co-extensive outwardly-expanded reduced wall portions in juxtaposition to enable said first and second flanges thereof to fixedly locate said annular stiffening memher with respect to said casing;

a plurality of stator vanes each having a tip end and a stub end, said stub end including a threaded portion, each of said vanes being positioned with its tip end projecting radially inwardly toward the casing axis and its stub end projecting radially outwardly through one of said pairs of radially aligned openings, being received in said second bushing member;

and means securing said vane stub end in said second bushing member for relative rotation with respect thereto including a cylindrical cup member having a flange adjacent one end thereof, a first cavity opening outwardly away from the casing, a seat portion at the bottom of said first cavity, a second cavity opening inwardly toward said casing, said second cavity having a locating fiat on a wall thereof, and a hollow neck portion joining said cavities, said vane stub end having a flattened portion adapted to register with said cavity fiat for combined movement of said cup member and said vane, bearing means inter-posed between said cup member and said second bushing member, and nut means adapted to engage said vane stub end threaded portion and contact said seat portion for retention of said stub end in said second bushing member.

References Cited UNITED STATES PATENTS 2,778,564 1/1957 Halford et al. 230-414 3,079,128 2/1963 Burge 253-78 X FOREIGN PATENTS 1,111,358 10/1955 France.

35 DONLEY I. STOCKING, Primary Examiner.

H. F. RADUAZO, Assistant Examiner. 

1. IN A GAS TURBINE ENGINE, A LIGHTWEIGHT STATOR ASSEMBLY COMPRISING: A STATOR CASING HAVING A PLURALITY OF CIRCUMFERENTIALLY SPACED OPENING FORMED THEREIN; A PLURALITY OF STATOR VANES DISPOSED WITHIN SAID STATOR CASING AND HAVING MOUNTING STUDS EXTENDING OUTWARDLY THROUGH SAID OPENINGS THEREIN; AN ANNULAR STIFFENING MEMBER POSITIONED AROUND SAID CASING TO STRENGTHEN SAID CASING, SAID ANNULAR MEMBER HAVING A PLURALITY OF OPENINGS RADIALLY ALIGNED WITH THE OPENINGS IN SAID CASING; AND MEANS FOR BOTH JOURNALING THE MOUNTING STUDS OF SAID VANES AND SECURING SAID STIFFENING MEMBERS TO SAID CASING, AND MEANS INCLUDING A PLURALITY OF PAIRS OF INNER AND OUTER TELESCOPICALLY ARRANGED BUSHING MEMBERS LOCATED WITHIN AND EXTENDING BETWEEN THE RESPECTIVELY ALIGNED OPENINGS OF SAID CASING AND SAID STIFFENING MEMBER, SAID PAIRS OF BUSHING MEMBERS EACH HAVING A FLANGE ON THE OUTER MEMBER THEREOF ENGAGING THE INNER SURFACE OF THE CASING, A FLANGE ON THE INNER MEMBER THEREOF ENGAGING THE OUTER SURFACE OF THE STIFFENING MEMBER, AND INTERLOCKED LATERALLY ENLARGED PORTIONS ON BOTH MEMBERS OF THE PAIR ON THE OUTER SURFACE OF THE ASSOCIATED OPENING IN SAID CASING, WHEREBY SAID PAIRS OF BUSHING MEMBERS ARE LOCKED IN PLACE AND SECURE SAID STIFFENING MEMBER TO SAID CASING, WITH THE INNER BUSHING MEMBERS FORMING JOURNALING SURFACES FOR ROTATABLY MOUNTING SAID STUDS OF THE STATOR VANES. 